The present invention relates to the peer-to-peer communication of one-to-one type, or in particular to a session relay apparatus in which the network operation policy for the relay nodes on the network can be set and canceled with the start or the end of the peer-to-peer communication as a motive.
The network operated and managed by a network provider such as a communication carrier or ISP (Internet Service Provider) is configured of a plurality of relay nodes interconnected for relay the user packets. In the network configured of the relay nodes, the network operation policy for controlling the route and the communication quality of the user packets is called simply as the policy. This policy is set for each application or each user in accordance with the priority or security of the packet relay operation. The relay nodes making up the network perform the process of relay the packets in accordance with the policy thus set.
The network has arranged therein a policy server for uniquely managing the policy, and this policy server reflects the policy in the network by distributing the policy to a multiplicity of relay nodes constituting the network. A well-known protocol for distributing the policy from the policy server is COPS (Common Open Policy Service) defined in the standard recommendation RFC (Request for Comments) prepared by IETF (Internet Engineering Task Force) and issued by IAB (Internet Architecture Board).
The network provider can set in a network, for example, a policy for priority control in which the packet of a specific user is repeated preferentially over the packets of the other users. In this case, the policy server classifies specific influent packets in the network into a plurality of priority control classes for the relay node called the edge node arranged in the network boundary, and distributes the policy for setting in the packet header the value called DSCP (Diffserv Code Point) corresponding to each priority control class. The edge node with this policy set therein determines whether the packets flowing into the network configured of the relay nodes meet the conditions set by the policy, and in the presence of a packet meeting the particular conditions, the DSCP value is set in the header of the packet in accordance with the priority control class assigned to the particular packet. Each relay node making up the network performs the priority control of the packets in accordance with the DSCP value set by the edge node.
An example of priority control of the packets with the DSCP value set by the edge node is described in JP-A-2000-253047. In the technique called Diffserv (Differentiated Services) described in this publication, the relay node called the core node arranged in the network transfers packets by priority control in accordance with the order of priority set in the DSCP value under the rules predetermined based on the DSCP value in the header of the received packet. This technique called Diffserv is used, as in the IP (Internet Protocol) telephone, to reduce the transfer delay in transmitting/receiving, on the IP network, the packets requiring the real time property such as audio packets and video packets.
In the peer-to-peer communication of one-to-one type like the IP telephone, on the other hand, a session is established between two communication terminals by a session control protocol typically including SIP (Session Initiation Protocol) defined in the standard recommendation RFC 3261, and the peer-to-peer communication conducted with real time data such as voice and image on the session thus established. The term “session” is defined as the period from the start to the end of the logical connection for communication executed between two communication terminals. Also, the term “peer-to-peer communication” is defined as a form of direct communication established between communication terminals without any server therebetween. In SIP, a session relay apparatus for relay the session control message searches for the terminal of the other party of communication, holds the information required for the peer-to-peer communication including the address of the communication terminal, the port number and the data number or otherwise executes the session management. The “session control message” repeated by the session control message is defined as a message transmitted or received prior to the start or end of the session between communication terminals.
In this peer-to-peer communication, the contents of the data transmitted and received between the communication terminals for each session may be different, include audio data or dynamic image data even in the communication between the same terminals. In such a case, packets are required to be repeated with the proper policy in accordance with the contents of the data, i.e. the contents of the communication. In the case where the network policy is controlled by the policy server as described above, the start and end of the peer-to-peer communication cannot be detected by the policy server, and therefore, the operator of the policy server is required to set the proper policy in accordance with the contents of the communication for the edge nodes in accordance with the start and end of the peer-to-peer communication. In this method, however, an increased network size requires frequent policy setting process, and therefore the setting by the operator may fail to meet the requirements.
In the method for setting in the edge nodes all the policies on the communication terminal for the peer-to-peer communication, on the other hand, the search process for the conditions of classification of the policy control in the edge nodes increases with the increase in the network scale. The increased search process imposes a processing burden on the edge nodes, resulting in an increased packet relay delay for real-time packets.